U.S. patent number 5,767,219 [Application Number 08/829,423] was granted by the patent office on 1998-06-16 for polysiloxane-polyether block copolymer and method for the preraration thereof.
This patent grant is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Masanao Kamei, Hiroshi Sasaki, Mitsuhiro Takarada.
United States Patent |
5,767,219 |
Takarada , et al. |
June 16, 1998 |
Polysiloxane-polyether block copolymer and method for the
preraration thereof
Abstract
Proposed is a novel polysiloxane-polyether block copolymer
having excellent heat resistance, which is characterized by the
molecular structure consisting of repetition of
diorganopolysiloxane units and polyoxyalkylene units having a
bisphenol linkage of the formula --O--Pn--CMe.sub.2 --Pn--O-- in
the unit, Pn being a 1,4-phenylene group and Me is a methyl group.
This polysiloxane-polyether block copolymer can be prepared by
conducting a hydrosilation reaction between a diorganopolysiloxane
terminated at each molecular chain end with a silicon-bonded
hydrogen atom and a polyoxyalkylene compound having the bisphenol
linkage in the molecule and terminated at each molecular chain end
with an alkenyl group or, preferably, allyl group in the presence
of a platinum catalyst. The stability of the block copolymer
obtained by the hydrosilation reaction can be further improved,
when the block copolymer has a silicon-bonded hydrogen atom as the
terminal group, by reacting the silicon-bonded hydrogen atom with
water or alcohol to be converted into a silanolic hydroxy group or
alkoxy group.
Inventors: |
Takarada; Mitsuhiro (Gunma-ken,
JP), Kamei; Masanao (Gunma-ken, JP),
Sasaki; Hiroshi (Gunma-ken, JP) |
Assignee: |
Shin-Etsu Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
13677314 |
Appl.
No.: |
08/829,423 |
Filed: |
March 31, 1997 |
Foreign Application Priority Data
|
|
|
|
|
Apr 1, 1996 [JP] |
|
|
8-078989 |
|
Current U.S.
Class: |
528/29; 528/15;
528/31; 528/43; 556/445 |
Current CPC
Class: |
C08G
77/46 (20130101) |
Current International
Class: |
C08G
77/00 (20060101); C08G 77/46 (20060101); C08G
077/08 () |
Field of
Search: |
;528/29,31,43,15
;556/445 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Glass; Margaret W.
Attorney, Agent or Firm: Millen, White, Zelano, &
Branigan, P.C.
Claims
What is claimed is:
1. A polysiloxane-polyether block copolymer having an alternate
repetition of the units:
(A) a first type block units of polysiloxane moiety represented by
the general formula
in which each R.sup.1 is, independently from the others, an
unsubstituted or halogen substituted monovalent hydrocarbon group
having 1 to 8 carbon atoms and the subscript m is a positive
integer in the range from 3 to 200, and
(B) a second type block units of polyether moiety represented by
the general formula
in which Pn is a 1,4-phenylene group, each R.sup.2 is,
independently from the other, a divalent hydrocarbon group having 2
to 8 carbon atoms, each R.sup.3 is, independently from the others,
an ethylene group or propylene group, each R.sup.4 is,
independently from the other, a hydrogen atom or methyl group and
each of the subscripts p and q is a positive integer in the range
from 3 to 30.
2. The polysiloxane-polyether block copolymer as claimed in claim 1
in which the group denoted by R.sup.1 is selected from the group
consisting of alkyl groups and aryl groups.
3. The polysiloxane-polyether block copolymer as claimed in claim 2
in which the group denoted by R.sup.1 is a methyl group.
4. The polysiloxane-polyether block copolymer as claimed in claim 1
in which the subscript m is a positive integer in the range from 5
to 100.
5. The polysiloxane-polyether block copolymer as claimed in claim 1
in which each of the subscripts p and q is a positive integer in
the range from 5 to 20.
6. The polysiloxane-polyether block copolymer as claimed in claim 1
in which the group denoted by R.sup.2 is selected from the group
consisting of propylene group, isobutylene group and
2-methylbutylene group.
7. A method for the preparation of a polysiloxane-polyether block
copolymer of claim 1 which comprises the steps of:
(a) mixing an organohydrogenpolysiloxane represented by the general
formula
in which each R.sup.1 is, independently from the others, an
unsubstituted or halogen substituted monovalent hydrocarbon group
having 1 to 8 carbon atoms and the subscript m is a positive
integer in the range from 3 to 200, and a polyether compound
represented by the general formula
in which Pn is a 1,4-phenylene group, each R.sup.3 is,
independently from the others, an ethylene group or propylene
group, each R.sup.4 is, independently from the other, a hydrogen
atom or methyl group, each R.sup.5 is a monovalent hydrocarbon
group having 2 to 8 carbon atoms and having an ethylenically
unsaturated linkage and each of the subscripts p and q is a
positive integer in the range from 3 to 30 to form a mixture;
(b) admixing the mixture with a catalytic amount of a platinum
compound; and
(c) heating the mixture to effect hydrosilation reaction between
the silicon-bonded hydrogen atoms at the molecular chain ends of
the organohydrogenpolysiloxane and the ethylenically unsaturated
linkages in the groups R.sup.5 at the molecular chain ends of the
polyether compound.
8. The method for the preparation of a polysiloxane-polyether block
copolymer as claimed in claim 7 in which the group denoted by
R.sup.5 is an allyl group.
9. The method for the preparation of a polysiloxane-polyether block
copolymer as claimed in claim 7 in which the platinum compound is
chloroplatinic acid or a complex thereof with a vinyl compound.
10. The method for the preparation of a polysiloxane-polyether
block copolymer as claimed in claim 7 in which the amount of the
platinum compound is in the range from 2 to 1000 ppm by weight as
platinum based on the amount of the organohydrogenpolysiloxane.
11. The method for the preparation of a polysiloxane-polyether
block copolymer as claimed in claim 7 in which the
organohydrogenpolysiloxane and the polyether compound are mixed in
a substantially equimolar proportion.
12. The method for the preparation of a polysiloxane-polyether
block copolymer as claimed in claim 7 in which the mixture of the
organohydrogenpolysiloxane and the polyether compound is heated in
step (c) at a temperature in the range from 50.degree. to
120.degree. C.
13. A method for the preparation of a terminal-stabilized
polysiloxane-polyether block copolymer of claim 1 which comprises
the steps of:
(a) mixing an organohydrogenpolysiloxane represented by the general
formula
in which each R.sup.1 is, independently from the others, an
unsubstituted or halogen substituted monovalent hydrocarbon group
having 1 to 8 carbon atoms and the subscript m is a positive
integer in the range from 3 to 200, and a polyether compound
represented by the general formula
in which Pn is a 1,4-phenylene group, each R.sup.3 is,
independently from the others, an ethylene group or propylene
group, each R.sup.4 is, independently from the other, a hydrogen
atom or methyl group, each R.sup.5 is a monovalent hydrocarbon
group having 2 to 8 carbon atoms and having an ethylenically
unsaturated linkage and each of the subscripts p and q is a
positive integer in the range from 3 to 30 to form a mixture;
(b) admixing the mixture with a catalytic amount of a platinum
compound;
(c) heating the mixture to effect hydrosilation reaction between
the silicon-bonded hydrogen atoms at the molecular chain ends of
the organohydrogenpolysiloxane and the ethylenically unsaturated
linkages in the groups R.sup.5 at the molecular chain ends of the
polyether compound forming a polysiloxane-polyether block copolymer
having at least one silicon-bonded hydrogen atom at the molecular
chain end;
(d) admixing the reaction mixture after step (c) with water or an
alcohol having 1 to 4 carbon atoms in a molecule; and
(e) heating the mixture at a temperature in the range from
50.degree. to 150.degree. C. for 1 to 6 hours to covert the
silicon-bonded hydrogen atom at the molecular chain end into a
hydroxy group or alkoxy group.
14. The method for the preparation of a terminal-stabilized
polysiloxane-polyether block copolymer as claimed in claim 13 in
which the amount of water or an alcohol added to the reaction
mixture after step (c) is at least a half mole per mole of the
silicon-bonded hydrogen atoms at the molecular chain ends of the
block copolymer obtained in step (c).
Description
BACKGROUND OF THE INVENTION
The present invention relates to a novel polysiloxane-polyether
block copolymer and a method for the preparation thereof. More
particularly, the invention relates to a block copolymer consisting
of alternate repetition of organopolysiloxane blocks and polyether
blocks and having usefulness as an antistatic agent, mold-release
or surface-release agent and lubricant with excellent heat
resistance as well as to an efficient method for the preparation of
such a block copolymer.
As is well known, diorganopolysiloxane oils or so-calledsilicone
oils in general have excellent heat resistance and exhibit good
releasability so that they are widely used as a mold release agent
on metal molds in the molding process of various kinds of
thermoplastic and thermosetting resins and rubbers and as a surface
release agent on toner particles used in electrophotographic
copying and printing machines. Besides the diorganopolysiloxane
oils, e.g., dimethylpolysiloxane oils, amino-modified or
polyether-modified diorganopolysiloxanes are widely used in molding
compositions based on epoxy resins, polystyrene resins, ABS resins
and the like as an additive ingredient such as a stress reducing
agent, internal mold release agent, impact strength improver or
antistatic agent.
Conventional dimethylpolysiloxane oils mentioned above, however,
are not quite satisfactory in respect of their heat resistance.
When the oil is used as a mold release agent on metal mold for
resin molding, for example, the oil is subject to gradual thermal
degradation at a temperature of 150.degree. C. or higher and
gelation of the oil takes place at a temperature of 200.degree. C.
or higher as is sometimes encountered in the resin molding
processes. Dimethylpolysiloxane oils are also not satisfactory as a
release agent for toner particles in a high-speed
electrophotographic copying machine because the heating roller of
the machine is run at a high temperature of 200.degree. C. or
higher to cause thermal degradation of the oil so that good
reproduction of images can hardly be accomplished.
On the other hand, a trend in recent years in the resin molding
technology and electrophotographic copying machines that the
working temperature of the metal mold or heating rollers is
increased higher and higher in order to improve the productivity of
resin molding or to decrease the copying time. Several attempts and
proposals have been made for the improvement of silicone oils to be
in compliance with the requirement for a higher service temperature
as a release agent including an amino group-containing
diorganopolysiloxane oil disclosed in Japanese Patent Kokai
3-227206 and mercapto group-containing diorganopolysiloxane oil
disclosed in Japanese Patent Kokai 4-320424. The solution of the
problems provided by these modified diorganopolysiloxane oils,
however, is still far from satisfactory because, in addition to the
insufficient improvement in the heat resistance of the oils, these
modified diorganopolysiloxane oils are susceptible to emission of
an unpleasant odor due to ammonia or mercaptan or discoloration by
heating if not to mention that little antistatic effect can be
obtained with these oils.
It is also a well established technology that various kinds of
resin compositions are admixed with a polyether-modified
diorganopolysiloxane or a quaternary ammonium compound with an
object to render the resin composition antistatic. Examples of the
polyether-modified diorganopolysiloxane include a
diorganopolysiloxane having polyoxyalkylene groups as the pendants
on the main chain of polysiloxane, a block copolymer consisting of
polyoxyalkylene blocks and diorganopolysiloxane blocks as disclosed
in Japanese Patent Kokai 4-234307 and complexes of a
polyoxyethylene-dimethylpolysiloxane-polyoxyethylene copolymer and
an alkali metal salt or alkaline earth metal salt as disclosed in
Japanese Patent Kokai 7-247413. Although these polyether-modified
dimethylpolysiloxanes are excellent as an antistatic agent, the
polyether moiety therein is susceptible to conversion into
aldehydes by heating so that their properties required for a
release agent are lost at all. Accordingly, they are not quite
satisfactory as a release agent or lubricant to be used under high
temperature conditions or, in other words, they cannot be used
under exposure to a high temperature of 150.degree. C. or higher as
is the case in high-temperature molding due to lack in the heat
resistance.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide a novel
silicone-based compound having excellent heat resistance and
suitable for use as a release agent, antistatic agent or lubricant
to satisfy the requirements for heat resistance as well as to
provide an efficient method for the preparation thereof Thus, the
silicone-based compound of the invention is a
polysiloxane-polyether block copolymer consisting of an alternate
repetition of two types of the units including:
(A) a first type block units of polysiloxane moiety represented by
the general formula
in which each R.sup.1 is, independently from the others, an
unsubstituted or substituted monovalent hydrocarbon group having 1
to 8 carbon atoms and the subscript m is a positive integer in the
range from 3 to 200, and
(B) a second type block units of polyether moiety represented by
the general formula
in which Pn is a 1,4-phenylene group, each R.sup.2 is,
independently from the other, a divalent hydrocarbon group having 2
to 8 carbon atoms, each R.sup.3 is, independently from the others,
an ethylene group or propylene group, each R.sup.4 is,
independently from the other, a hydrogen atom or methyl group and
each of the subscripts p and q is a positive integer in the range
from 3 to 30.
The above defined polysiloxane-polyether block copolymer can be
prepared by a method which comprises the steps of:
(a) mixing an organohydrogenpolysiloxane represented by the general
formula
in which each symbol has the same meaning as defined above, and a
polyether compound represented by the general formula
in which R.sup.5 is a monovalent hydrocarbon group having 2 to 8
carbon atoms and having an ethylenically unsaturated linkage, which
is preferably an alkenyl group of the general formula --(--CH.sub.2
--).sub.n --CR.dbd.CH.sub.2, R being a hydrogen atom or a methyl
group and n being a positive integer of 1 to 6 or, more preferably,
an allyl group, and each of the other symbols has the same meaning
as defined above, to form a mixture;
(b) admixing the mixture with a catalytic amount of a platinum
compound; and
(c) heating the mixture to effect hydrosilation reaction between
the silicon-bonded hydrogen atoms at the molecular chain ends of
the organohydrogenpolysiloxane and the ethylenically unsaturated
linkages in the groups R.sup.5 at the molecular chain ends of the
polyether compound.
Each of the molecular chain ends of the block copolymer obtained by
the above defined method is terminated either with a silicon-bonded
hydrogen atom of the organohydrogenpolysiloxane or an alkenyl group
R.sup.5 of the polyether compound depending on the blending
proportion of the organohydrogenpolysiloxane and polyether
compound. When the molecular chain end of the block copolymer is
terminated by a silicon-bonded hydrogen atom, it is preferable that
the block copolymer obtained in step (c) of the above defined
method is further reacted with water or an alcohol having 1 to 4
carbon atoms in a molecule to give a terminal-stabilized block
copolymer.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1, 2 and 3 are each an infrared absorption spectrum of the
block copolymer obtained in Example 1, Example 2 and Comparative
Example, respectively.
FIGS. 4, 5 and 6 are each a TG-DTA diagram of the block copolymer
obtained in Example 1, Example 2 and Comparative Example,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polysiloxane-polyether block copolymer of the present invention
has a molecular structure consisting of alternate repetition of the
polysiloxane units represented by the above given general formula
(1), referred to as the units A hereinafter, and the
polyoxyalkylene units represented by the above given general
formula (2), referred to as the units B hereinafter. In the general
formula (1) representing the unit A, each R.sup.1 is, independently
from the others, an unsubstituted or substituted monovalent
hydrocarbon group free from aliphatic unsaturation and having 1 to
8 carbon atoms, which is exemplified by alkyl groups such as
methyl, ethyl, propyl, butyl, hexyl and octyl groups and aryl
groups such as phenyl and tolyl groups as well as
halogen-substituted alkyl groups such as 3,3,3-trifluoropropyl
group, of which methyl and phenyl groups are preferable from the
standpoint of industrial preparation of the block copolymer. When
excellent mold releasability and lubricity are desired for the
block copolymer, in particular, it is preferable that all of or at
least 50% by moles of the groups denoted by R.sup.1 are methyl
groups. The subscript m in the general formula (1) is a positive
integer, by which the chain length of the unit A is defined, in the
range from 3 to 200 or, preferably, from 5 to 100. When the value
of m is too small, the block copolymer cannot be imparted with high
heat resistance while, when the value of m is too large, the block
copolymer has an increased viscosity to cause a disadvantage in the
applications in which fluidity of the block copolymer is
desirable.
The polyoxyalkylene unit, i.e. unit B, is represented by the
general formula (2) given above, in which Pn is a 1,4-phenylene
group, R.sup.4 is a hydrogen atom or a methyl group and each
R.sup.2 is, independently from the others, a divalent hydrocarbon
group or, preferably, alkylene group having 2 to 8 carbon atoms
exemplified by ethylene, propylene, butylene, hexamethylene,
octamethylene and isobutylene groups, of which particularly
preferable are an n-propylene group of the formula --CH.sub.2
CH.sub.2 CH.sub.2 --, isobutylene group of the formula --CH.sub.2
CH(CH.sub.3)CH.sub.2 -- and 2-methylbutylene group of the formula
--CH.sub.2 CH(CH.sub.3)CH.sub.2 CH.sub.2 --. Each R.sup.3 in the
general formula (2) is, independently from the others, an ethylene
group --CH.sub.2 CH.sub.2 -- or propylene group --CH.sub.2
CH(CH.sub.3)-- either singly or as a combination of both so that
the polyether linkage has a structure of polyoxyethylene,
polyoxypropylene or poly(oxyethylene-oxypropylene). Each of the
subscripts p and q, which defines the number of repetition of the
oxyalkylene linkages, is a positive integer in the range from 3 to
30 or, preferably, from 5 to 20. When the values of p and q do not
fall within this range, the block copolymer would not be suitable
for certain applications. For example, no sufficiently high
antistatic effect can be obtained when the values of p and/or q are
too small while the block copolymer cannot be highly heat resistant
when the values are too large.
Since the polysiloxane-polyether block copolymer of the present
invention is formed by an alternate repetition of the units A and
units B, each of the molecular chain ends can be terminated either
with the unit A or with the unit B so that the block copolymer can
be represented by the formula (AB).sub.t, A(BA).sub.t or
B(AB).sub.t. When the molar proportion of the starting
organohydrogenpolysiloxane and the polyether compound is equimolar,
the resultant block copolymer has a structure of (AB)t while the
structure is A(BA).sub.t or B(AB).sub.t when the molar amount of
the organohydrogenpolysiloxane is larger or smaller, respectively,
than the polyether compound. The subscript t is the number of
alternation of the units A and B, preferably, in the range from 1
to 20. The value of t can be adequately controlled by interrupting
proceeding of the hydrosilation reaction at an appropriate stage
although the reaction cannot proceed too far due to the limitation
in the reaction rate and steric hindrance. When the value of t is
too large, the block copolymer has an increased viscosity to cause
a disadvantage of decreased workability in the applications in
which fluidity of the block copolymer is desirable. The terminal
group at each of the molecular chain ends of the block copolymer
can be a hydrogen atom, hydroxy group, alkoxy group having 1 to 4
carbon atoms, monovalent hydrocarbon group having 1 to 8 carbon
atoms, optionally, having an aliphatic unsaturation or
trialkylsiloxy group without particular limitations.
The above defined polysiloxane-polyether block copolymer of the
invention can be prepared by subjecting an
organohydrogenpolysiloxane represented by the above given general
formula (3) and a polyether compound represented by the above given
general formula (4) to the hydrosilation reaction in the presence
of a catalytic amount of a platinum compound as the catalyst.
The hydrosilation reaction can proceed either in the absence or in
the presence of an organic solvent. It is, however, advantageous,
when the polyether compound has a high viscosity or is a solid, to
use an organic solvent including aromatic hydrocarbon solvents and
ether solvents such as toluene, xylene, tetrahydrofuran, diethyl
ether, dibutyl ether and the like, in which the
organohydrogenpolysiloxane and the polyether compound are dissolved
together with the platinum catalyst. Suitable platinum compounds
include those in which the platinum atom is in the state of
zero-valency or tetravalency exemplified by chloroplatinic acid and
complexes thereof with a vinyl compound. The amount of the platinum
compound as the catalyst for the hydrosilation reaction is in the
range from 2 to 1000 ppm by weight or, preferably, from 5 to 200
ppm by weight relative to the amount of the
organohydrogenpolysiloxane of the general formula (3) as calculated
for the platinum atoms. Although the hydrosilation reaction can
proceed at a temperature in the range from room temperature to
150.degree. C., it is preferable that the reaction mixture is
heated at a temperature in the range from 50 to 120.degree. C. so
that the reaction is complete usually within 2 to 24 hours with
termination of viscosity increase of the reaction mixture.
The molecular chain end of the block copolymer after completion of
the above mentioned hydrosilation reaction is terminated with a
silicon-bonded hydrogen atom, i.e. hydrosilyl group, derived from
the organohydrogenpolysiloxane or an alkenyl group derived from the
alkenyl-terminated polyether compound depending on the blending
proportion of the two reactants. When the block copolymer has a
silicon-bonded hydrogen atom at the molecular chain end as is the
case when the block copolymer formed by the hydrosilation reaction
has a structure of (AB).sub.t or A(BA).sub.t mentioned before, it
is advantageous from the standpoint of stability of the block
copolymer that the silicon-bonded hydrogen atom is converted into a
silanolic hydroxy group,trimethylsiloxy group or alkoxy group by
the reaction with water or an alcohol having 1 to 4 carbon atoms in
a molecule such as methyl, ethyl and isopropyl alcohols. The molar
amount of water or lower alcohol to be added to the reaction
mixture is at least a half of the silicon-bonded hydrogen atoms in
the block copolymer. This stabilization treatment is performed by
admixing the reaction mixture after completion of the hydrosilation
reaction with an appropriate amount of water or alcohol and heating
the mixture at 50 to 150.degree. C. for 1 to 6 hours so that the
hydrosilyl groups are dehydrogenated by the activity of the
remaining platinum catalyst in the reaction mixture and converted
into a silanol group or alkoxysilyl group by reacting with water or
alcohol. As is well known, the silanolic hydroxy group can be
converted into a trimethylsiloxy group by the trimethylsilylation
reaction with hexamethyldisilazane or trimethyl chlorosilane with
an object to further increase stability of the block copolymer.
The organohydrogenpolysiloxane as one of the reactants in the
hydrosilation reaction and represented by the general formula (3)
is exemplified by those expressed by the following formulas, though
not particularly limitative thereto:
H--(--SiMe.sub.2 --O--).sub.9 --SiMe.sub.2 --H;
H--(--SiMe.sub.2 --O--).sub.19 --SiMe.sub.2 --H;
H--(--SiMe.sub.2 --O--).sub.39 --SiMe.sub.2 --H;
H--(--SiMe.sub.2 --O--).sub.7 --(--SiPh.sub.2 --O--).sub.2
--SiMe.sub.2 --H;
H--(--SiMe.sub.2 --O--).sub.7 --(--SiMePh--O--).sub.2 --SiMe.sub.2
--H;
H--(--SiMe.sub.2 --O--).sub.15 --(--SiPh.sub.2 --O--).sub.4
--SiMe.sub.2 --H;
H--(--SiMe.sub.2 --O--).sub.15 --(--SiMePh--O--).sub.4 --SiMe.sub.2
--H;
H--(--SiMe.sub.2 --O--).sub.59 --SiMe.sub.2 --H; and
H--SiMe.sub.2 --O--(--SiMePh--O--).sub.18 --SiMe.sub.2 --H,
in which Me and Ph denote a methyl group and a phenyl group,
respectively. These organohydrogenpolysiloxanes can be prepared by
a known method such as an acid-catalyzed siloxane rearrangement
equilibration reaction between 1,1,3,3-tetramethyldisiloxane and a
cyclic dimethyl-, diphenyl- or methylphenylpolysiloxane
oligomer.
The polyether compound as the other reactant and represented by the
general formula (4) given above can be obtained by the alkenylation
reaction of an alcoholic hydroxy-terminated polyether compound
derived from bisphenol A as a commercial product such as Uniol
polyethers sold by Nippon Oils and Fats Co. and those sold by Sanyo
Chemical Industries, Ltd. as an addition product of bisphenol A and
a polyoxyalkylene. Alkenyl-terminated polyethers are available on
the market and can be used as such including Uniox DAA-780 sold by
Nippon Oils and Fats Co. and DABP polyethers sold by Sanyo Chemical
Industries, Ltd, though not particularly limitative thereto.
The polyether compound suitable as the reactant in the
hydrosilation reaction is exemplified by those expressed by the
following formulas: ##STR1## in which Pn is a 1,4-phenylene group
and Me is a methyl group.
The polysiloxane-polyether block copolymer of the present invention
obtained in the above described manner is usually a fluid having a
viscosity in the range from 50 to 1,000,000 centistokes at
25.degree. C. or in the form of solid at room temperature. Though
dependent on the particularly intended application, it is
advantageous that the block copolymer has a viscosity in the range
from 100 to 50,000 centistokes at 25.degree. C. for most
applications in respect of workability.
The polysiloxane-polyether block copolymer of the invention has
remarkably high heat resistance as compared with conventional
polyether-modified organopolysiloxanes in which the polyoxyalkylene
groups are bonded to the siloxane units as a pendant group thereon
as is represented, for example, by the general formula:
in which Me is a methyl group, G is a polyoxyalkylene group of the
formula --CH.sub.2 CH.sub.2 CH.sub.2 O(C.sub.2 H.sub.4 O).sub.y H,
y being a positive integer of 1 to 30, and the subscripts w and x
are each a positive integer of 1 to 500 and 1 to 50, respectively.
This remarkably high heat resistance of the block copolymer is
presumably due to the facts that the terminal of the
polyoxyalkylene unit is blocked with a siloxane unit and the
polyoxyalkylene unit has a structure of bisphenol A known to be
thermally stable. By virtue of the polyoxyalkylene moiety contained
therein, the block copolymer of the invention has good
compatibility with various kinds of other resinous materials and
has a low volume resistivity to have usefulness as an antistatic
agent.
Having the above mentioned unique properties, the block copolymer
of the present invention is useful in a variety of applications
including mold release agents on a metal mold for molding of
synthetic resins and rubbers, release agents for toner particles in
electrophotographic copying machines, oiling agents of synthetic
fibers such as oiling agents for base fibers, fibers for false
twisting, base carbon fibers and tire cord filaments, antistatic
agents for various kinds of fabric materials, impact strength
improvers and mold-release additives in thermoplastic resin based
molding compositions, stress reducing agents in epoxy resin-based
molding compositions, lubricants in polishing waxes, heating media
and so on.
Moreover, the polysiloxane-polyether block copolymer of the
invention has excellent heat resistance without suffering
discoloration and changes in the volume resistivity even after
prolonged heating in air so that the block copolymer is
particularly useful as a release agent in copying machines operated
at high temperatures and an additive such as mold release agent or
antistatic agent in molding compositions based on a thermoplastic
resin which must be processed at a high temperature such as
polyethylene terephthalate, polyphenylene oxide, polycarbonate and
the like. This feature is particularly advantageous as compared
with conventional organopolysiloxane oils for high temperature use
which are inherently colored or subject to discoloration within a
short time at high temperatures as a consequence of admixture of
heat resistance improvers such as amine compounds, phenolic
compounds, iron-containing compounds, cerium-containing compounds
and the like.
In the following, the polysiloxane-polyether block copolymer of the
present invention and the method for the preparation thereof are
described in more detail by way of Examples, in which the term of
"parts" always refers to "parts by weight".
Example 1.
A reaction mixture was prepared in a flask by introducing 78.8
parts of a dimethyl hydrogenpolysiloxane expressed by the
formula
in which Me is a methyl group, and 90 parts of an allyl-terminated
polyoxyethylene (Uniox DAA-780, supra) expressed by the formula
##STR2## in which Pn is a 1,4-phenylene group, together with 0.1
part of a platinum catalyst containing 0.5% by weight of platinum
(PL-50T, a product by Shin-Etsu Chemical Co.) and the mixture was
heated at 80.degree. C. for 5 hours under agitation to effect the
hydrosilation reaction. When no further increase was noted in the
reaction mixture after the end of this reaction time indicating
completion of the hydrosilation reaction, the reaction mixture in
the flask was admixed with 10 parts of water and further agitated
at 80.degree. C. for 2 hours followed by removal of water by
heating the mixture at 110.degree. C. for 2 hours under a reduced
pressure of 5 mmHg.
The thus obtained product, which was a clear and colorless oily
liquid and is referred to as the block copolymer 1 hereinafter, had
properties including a viscosity of 9500 centistokes at 25.degree.
C., refractive index of 1.457 at 25.degree. C., volume resistivity
of 8.times.1010.sup.10 ohm.multidot.cm at 25.degree. C. and
weight-average molecular weight of 17,000 as determined by the gel
permeation chromatographic method making reference to known
polystyrene samples. FIG. 1 of the accompanying drawing shows the
infrared absorption spectrum of the block copolymer 1.
The block copolymer 1 could be assumed to have a block-wise
structure consisting of t times repetition of the units of the
formula ##STR3## in which the subscript t had an average value of
approximately 12.
With an object to test the heat resistance, the block copolymer 1
was heated in air at 200.degree. C. for 100 hours so that the oil
turned slightly yellowish and the viscosity thereof was decreased
to 11,000 centistokes at 25.degree. C. with a weight loss of 19.6%.
FIG. 4 is a diagram obtained by TG-DTA
(thermogravimetric-differential thermal analysis) undertaken in air
at a rate of temperature elevation of 10.degree. C. per minute.
Example 2.
The procedure for the preparation of a block copolymer, referred to
as the block copolymer 2 hereinafter, was substantially the same as
in Example 1 for the preparation of the block copolymer 1 except
that the reaction mixture for the hydrosilation reaction was
prepared from 132 parts of a dimethyl hydrogenpolysiloxane
expressed by the formula
in which Me is a methyl group, 75 parts of the same
allyl-terminated polyoxyethylene as used in Example 1 and 0.1 part
of the same platinum catalyst.
The thus obtained product was a clear and colorless oily liquid and
had properties including a viscosity of 16,000 centistokes at
25.degree. C., refractive index of 1.445 at 25.degree. C., volume
resistivity of 2.times.10.sup.11 ohm.multidot.cm at 25.degree. C.
and weight-average molecular weight of 24,000 as determined by the
gel permeation chromatographic method. FIG. 2 of the accompanying
drawing shows the infrared absorption spectrum of the block
copolymer 2.
The block copolymer 2 could be assumed to have a block-wise
structure consisting of t times repetition of the units of the
formula ##STR4## in which the subscript t had an average value of
approximately 10.5.
The block copolymer 2 was heated in air at 200.degree. C. for 100
hours so that the oil turned slightly yellowish and the viscosity
thereof was decreased to 14,000 centistokes at 25.degree. C. with a
weight loss of 10.2%. FIG. 5 is a diagram obtained by TG-DTA
undertaken under the same conditions as in Example 1.
Example 3.
The procedure for the preparation of a block copolymer, referred to
as the block copolymer 3 hereinafter, was substantially the same as
in Example 1 for the preparation of the block copolymer 1 except
that the reaction mixture for the hydrosilation reaction was
prepared from 70 parts of the same dimethyl hydrogenpolysiloxane as
used in Example 2, 60 parts of a second allyl-terminated
polyoxyethylene expressed by the formula ##STR5## and 0.1 part of
the same platinum catalyst.
The thus obtained product was a clear and colorless oily liquid and
had properties including a viscosity of 19,000 centistokes at
25.degree. C., refractive index of 1.450 at 25.degree. C., volume
resistivity of 3.times.10.sup.10 ohm.multidot.cm at 25.degree. C.
and weight-average molecular weight of 28,000 as determined by the
gel permeation chromatographic method.
The block copolymer 3 could be assumed to have a block-wise
structure consisting of t times repetition of the units of the
formula ##STR6## in which the subscript t had an average value of
approximately 10.4.
The block copolymer 3 was heated in air at 200.degree. C. for 100
hours so that the oil turned slightly yellowish and the viscosity
thereof was decreased to 17,000 centistokes at 25.degree. C. with a
weight loss of 9.5%.
Comparative Example.
The procedure for the preparation of a block copolymer, referred to
as the block copolymer 4 hereinafter, was substantially the same as
in Example 1 for the preparation of the block copolymer 1 except
that the reaction mixture for the hydrosilation reaction was
prepared from 131 parts of the same dimethyl hydrogenpolysiloxane
as used in Example 1, 100 parts of a polyether compound expressed
by the average formula
(Uniox AA-480R, a product by Nippon Oils and Fats Co.) and 0.1 part
of the same platinum catalyst.
The thus obtained product was a clear and colorless oily liquid and
had properties including a viscosity of 600 centistokes at
25.degree. C., refractive index of 1.436 at 25.degree. C., volume
resistivity of 4.times.10.sup.11 ohm.times.cm at 25.degree. C. and
weight-average molecular weight of 16,000 as determined by the gel
permeation chromatographic method. FIG. 3 of the accompanying
drawing shows the infrared absorption spectrum of the block
copolymer 4.
The block copolymer 4 could be assumed to have a block-wise
structure consisting of t times repetition of the units of the
formula
in which the subscript t had an average value of approximately
13.3.
The block copolymer 4 was found to be completely gelled when it was
heated in air at 200.degree. C. for 100 hours. FIG. 6 is a diagram
obtained by TG-DTA undertaken under the same conditions as in
Example 1.
* * * * *